Ionic salt residue on the surface of a substrate material is a reoccurring problem. In particular, printed circuit boards are prone to heavy salt deposit concentrations following the soldering precess. Printed circuit boards are manufactured in mass by a process known as wave soldering. Prior to the soldering process, a liquid flux compound is applied to the boards to insure proper adhesion of the solder joints. The flux compounds can be rosin acid based, organic acids or synthetically activated. The heat of the soldering process causes the component materials of the flux compound to decompose thereby liberating inorganic acids which react with any oxides present on the circuit board. The reaction insures solderability by removing the oxides, but the reaction produces ionic salts which are deposited on the printed circuit boards. The salt deposits are a problem because they can be corrosive. Moreover, a salt deposit can act as a bridge that can short circuit the board.
Printed circuit boards and other objects which must be free of salt deposits are cleaned in commercial washing processes, which can be batch or in-line processes. Most commercial processes consist of multiple steps in which the surface is submerged and sprayed with a cleaning solution, and then rinsing the objects with pure cleaning solution. Organic solvents or aqueous solutions can be used as cleaning solutions, but the organic solvent must have a low polarity because polar solvents are too flammable to be safely used in commercial processes. However, organic solvents having a low polarity are inefficient at solvating ionic salt residue, and when used as the cleaning solution, a significant amount of ionic salt residue remains undissolved. Therefore, the wash process must be repeated over and over again which increases production cost. Alcohol is sometimes added to low-polar solvents as a cosolvent, but higher concentrations of alcohol can be dangerous because it is so flammable. Likewise, aqueous solutions are inefficient because the high surface tension of water based solutions prevents effective cleaning where the line spacings are less than about 1 mil. Moreover, aqueous solutions are largely ineffective at dissolving organic rosin acids.
Therefore, a need exists for a method for cleaning salt deposits from objects that is efficient and safe. The method should provide nearly complete removal of ionic salt residue in a single cleaning cycle. A need also exists for a cleaning composition that is effective at removing ionic salt deposits with a single cleaning cycle. The composition should be of a low polarity so that it can be safely used in commercial processes.